Effect of internal structure installed in pressure vessel in HFO-1123 disproportionation reaction

Abstract

Trifluoroethylene (HFO-1123) has been attracting considerable attention as a promising low-global-warming-potential refrigerant for new residential split air conditioners. However, if the refrigerant compressor short circuits, the disproportionation reaction of HFO-1123 may propagate under high-temperature and high-pressure conditions, which may lead to compressor explosion. Studies seeking to suppress the disproportionation reaction by adding refrigerants that do not cause the disproportionation HFO-1123 reaction have been performed; two refrigerant mixtures have been proposed as next-generation refrigerants. However, these mixtures could not suppress the disproportionation reaction under the worst condition (150 °C, 6.0 MPa) in practical use. Consequently, the difference in the reaction propagations between the experimental vessel and actual compressor for further suppression was investigated in this study. The experiment was conducted by introducing an internal part that mimics the actual compressor into the vessel. We investigated whether the flame ignited at the bottom of the vessel would pass through a small slit installed in the center and propagate to the entire vessel. The parameters were the volume of the ignition space and the width and thickness of the slit. When a combustion flame passes through a narrow gap, it may be cooled by a solid wall and extinguished. It was expected that the flame would be cooled and extinguished when passing through a narrow space, even in the disproportionation reaction. It was found that the reaction suppression effect was significant when the slit width was 1 mm or less.